During Thursday's sentencing remarks, District Court judge Stanley Chan said police had banned the vigil to protect public safety and order, but the defendants could be seen entering Victoria Park and chanting slogans despite repeated police warnings.

He said while Hong Kong's constitution protects freedom of assembly, such rights are not absolute. "From the very beginning, the public meeting was unauthorized," Chan said. He criticized participants of the vigil for believing "they can enjoy more freedom than others."

Chan also said Wong, as a prominent activist, did not have a passive role in the vigil and added the court must impose a penalty with a deterrent effect.

Ahead of Thursday's sentencing, dozens of supporters and journalists were seen queuing for a seat in the public gallery. The court also opened an extension room to accommodate the crowd.

Iconic commemoration

The event remains one of the most tightly censored topics in mainland China, with discussions of it scrubbed from mass media. Chinese authorities have not released an official death toll, but estimates range from several hundred to thousands.

That any commemoration could be held in Hong Kong was often seen as iconic of the city's autonomy from China, a litmus test for political freedoms in the special administrative region.

However, the introduction last year of a national security law -- which criminalizes secession, subversion and collusion with foreign forces with a maximum penalty of life imprisonment -- has threatened the future of the candlelight vigil. The law came into force less than a month after the last June 4 vigil.

The Hong Kong Alliance in Support of Patriotic Democratic Movements of China, which organizes the annual event, has been calling for an end to one-party rule, a slogan that may fall foul of the national security law.